Tuesday, March 8, 2011
Perfect Your Approaches
Nonprecision suggests a casual approach to IFR procedures, but you’d best fly them with precision
Traditional wisdom has it that all approaches should be timed, but few pilots bother to time an ILS. Conversely, timing is absolutely essential on a nonprecision procedure. The only question is how to time an approach and what time should be used for the termination of the effort and the beginning of the miss. More on that later.
While examining the approach plate, check out the times listed at the bottom of the chart and decide at what speed you'll make the approach. Keep in mind that faster approaches are more difficult to keep on track, so select the slowest approach speed consistent with conditions and your airplane's capabilities. Unless you're operating a biz jet, there's rarely any reason to fly an approach faster than 120 knots, never mind the 747 coming up behind you. Most singles and light twins can handle 90-100 knots with ease. (Interestingly, the recently introduced Cessna Mustang uses a reference speed of 95-100 knots on approach.)
Since you're unlikely to receive much help from radar in areas where NPAs are the rule, you should be especially aware of the minimum sector altitudes. Make a mental note of the MDA, as well, and any obstacles on either side of the approach course, just to get a feel of the consequences of deviating left or right. (Ketchikan, Alaska's airport, for example, is built on the south side of a steep mountain. If you wander too far right while flying into runway 29, you'll never have to worry about doing it again.)
If the atmospherics are near minimums, pay careful attention to the miss procedure well before you might need it. If nothing else, at least memorize the initial heading and altitude. Be familiar with the layout of the airport, especially if there's a chance you may be required to make a circling approach.
NPAs can guide an aircraft to minimums as low as a 350-foot ceiling with 3⁄4-mile visibility, and may be installed where geographic obstructions or other ground obstacles make an ILS impossible.If the approach does terminate in a circle-to-land, you'll be expected to maintain at least 300 feet above the ground until you're lined up with the runway. Circling approaches in hard IFR is bad news, especially when the weather is at or near minimums. Most airplanes don't enjoy flying slow even in good weather, and the majority of pilots feel the same. A circling situation often sets a pilot up for a fall. He can't increase his speed too much or he'll only have to reduce it again for landing. Additionally, he needs to keep his turn fairly tight to stay close to the airport and maintain contact with the runway. Here again, speed control is critical, as a slower speed and steeper bank angle will increase the possibility of an accelerated stall.
As with an ILS, the primary risk is of the dreaded duck-under, but it's even more critical on an NPA because course guidance is less accurate. Accordingly, the consequences of dropping below the MDA can be considerably more severe than when flying an ILS. There's far more room for error on an NPA, both because the approach must be timed and flown at a constant airspeed and because the approach aid is often less accurate. Some pilots who fly a regular diet of NPA procedures buy a red, single-hand altitude reminder that adheres to the glass on the altimeter face and can be set to the appropriate MDA.
In emergency situations on precision approaches, pilots have been known to bust minimums and take an ILS all the way to the ground. If you pull it off and walk away without breaking anything, the consequences may be no more severe than a talk with the local FSDO. Like most pilots, I've flown ILSs to the flare several times during training under the hood with instructor Gary Meermans in the right seat. Sadly, the reality is that most of us will never be as good as we were right after earning our instrument rating. Flying an actual nonprecision approach to the runway during extremely low weather is about as dumb as the man who drowned while trying to walk around the world.
Two points need to be made about approach timing. You can't expect to arrive at the MAP (missed approach point) at the proper time unless you start the clock when you cross the FAF (final approach fix). Similarly, you must fly the approach at the planned speed, or the time becomes irrelevant.
The first task sounds simple enough, but Murphy's Law often manages to get in the way. Like most instrument pilots, I was taught the seven Ts of an IFR approach, especially apropos to a nonprecision effort: time, turn, tach, track, trim, tune, talk. After you say it a few times, it has a certain symmetry that makes it easy to remember.
Note that "time" is the first priority. When passing the FAF, be sure to punch the stopwatch immediately after you pass the fix. If it's a VOR, wait for a definite flag flip; if it's an NDB, wait for a full needle reversal. Since you're flying into an airport environment which, by definition, should be flatter than the surrounding terrain, you need to arrive on time, but if not, it's probably better to be a few seconds late than early.
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